Try and find the sections you are struggling with, see if maybe you do not understand some base level concepts (fractions, algebra, etc.) . Also, if you do not already have one develop a love for maths (if possible). Also, practice, practice, practice. NEVER underestimate it. For the next few months live, breath, eat and sleep mathematics. Find a few good tutorials or books, I hear Khan academy has quite good tutorials.

Also, you did not mention what level you were on i.e. what you are doing in maths: trig, algebra, calculus, etc.

is this an actual grade or a typo? cause if it is, it blew my mind, never seen E used before.

just remeber, if you study computer science on your own and you do end up taking it later, you will be ahead of everyone and have an easier time understanding it, so dont let it worry you too much, people learn at their own pace

I am now the #1 in my class in college in programming and maths, pass I got ~60% in maths in high school ONLYnow I understand maths better then ever!, I help/tech my younger brother and sisters in there home works, and now applying for math teacher job in school.

wish me good luck in the job.

EDIT

one more thing, to be good in maths you need to love maths, and spend your fun time solving maths questions